checkpatch: check line endings in text format files

Firmware may be included in the kernel as .ihex files.  These are
inherantly text, but not source.  The line ending checks are applicable to
these kinds of file, allow just these checks to apply to all files.

Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>